Product details

Function Counter Bits (#) 4 Technology family HC Supply voltage (min) (V) 2 Supply voltage (max) (V) 6 Input type Standard CMOS Output type Push-Pull Features Balanced outputs, High speed (tpd 10-50ns), Positive input clamp diode Operating temperature range (°C) -55 to 125 Rating Military
Function Counter Bits (#) 4 Technology family HC Supply voltage (min) (V) 2 Supply voltage (max) (V) 6 Input type Standard CMOS Output type Push-Pull Features Balanced outputs, High speed (tpd 10-50ns), Positive input clamp diode Operating temperature range (°C) -55 to 125 Rating Military
CDIP (J) 16 135.3552 mm² 19.56 x 6.92 LCCC (FK) 20 79.0321 mm² 8.89 x 8.89
  • Wide Operating Voltage Range of 2 V to 6 V
  • Outputs Can Drive Up To 10 LSTTL Loads
  • Low Power Consumption, 80-µA Max ICC
  • Typical tpd = 13 ns
  • ±4-mA Output Drive at 5 V
  • Low Input Current of 1 µA Max
  • Single Down/Up Count-Control Line
  • Look-Ahead Circuitry Enhances Speed of Cascaded Counters
  • Fully Synchronous in Count Modes
  • Asynchronously Presettable With Load Control

  • Wide Operating Voltage Range of 2 V to 6 V
  • Outputs Can Drive Up To 10 LSTTL Loads
  • Low Power Consumption, 80-µA Max ICC
  • Typical tpd = 13 ns
  • ±4-mA Output Drive at 5 V
  • Low Input Current of 1 µA Max
  • Single Down/Up Count-Control Line
  • Look-Ahead Circuitry Enhances Speed of Cascaded Counters
  • Fully Synchronous in Count Modes
  • Asynchronously Presettable With Load Control

The ’HC191 devices are 4-bit synchronous, reversible, up/down binary counters. Synchronous counting operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when instructed by the steering logic. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple-clock) counters.

The outputs of the four flip-flops are triggered on a low- to high-level transition of the clock (CLK) input if the count-enable (CTEN)\ input is low. A high at CTEN\ inhibits counting. The direction of the count is determined by the level of the down/up (D/U\) input. When D/U\ is low, the counter counts up, and when D/U\ is high, it counts down.

These counters feature a fully independent clock circuit. Change at the control (CTEN\ and D/U\) inputs that modifies the operating mode have no effect on the contents of the counter until clocking occurs. The function of the counter is dictated solely by the condition meeting the stable setup and hold times.

These counters are fully programmable; that is, each of the outputs can be preset to either level by placing a low on the load (LOAD)\ input and entering the desired data at the data inputs. The output changes to agree with the data inputs independently of the level of CLK. This feature allows the counters to be used as modulo-N dividers simply by modifying the count length with the preset inputs.

Two outputs are available to perform the cascading function: ripple clock (RCO)\ and maximum/minimum (MAX/MIN) count. MAX/MIN produces a high-level output pulse with a duration approximately equal to one complete cycle of the clock while the count is zero (all outputs low) counting down, or maximum (9 or 15) counting up. RCO\ produces a low-level output pulse under those same conditions, but only while CLK is low. The counters can be cascaded easily by feeding RCO\ to CTEN\ of the succeeding counter if parallel clocking is used, or to CLK if parallel enabling is used. MAX/MIN can be used to accomplish look ahead for high-speed operation.

The ’HC191 devices are 4-bit synchronous, reversible, up/down binary counters. Synchronous counting operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when instructed by the steering logic. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple-clock) counters.

The outputs of the four flip-flops are triggered on a low- to high-level transition of the clock (CLK) input if the count-enable (CTEN)\ input is low. A high at CTEN\ inhibits counting. The direction of the count is determined by the level of the down/up (D/U\) input. When D/U\ is low, the counter counts up, and when D/U\ is high, it counts down.

These counters feature a fully independent clock circuit. Change at the control (CTEN\ and D/U\) inputs that modifies the operating mode have no effect on the contents of the counter until clocking occurs. The function of the counter is dictated solely by the condition meeting the stable setup and hold times.

These counters are fully programmable; that is, each of the outputs can be preset to either level by placing a low on the load (LOAD)\ input and entering the desired data at the data inputs. The output changes to agree with the data inputs independently of the level of CLK. This feature allows the counters to be used as modulo-N dividers simply by modifying the count length with the preset inputs.

Two outputs are available to perform the cascading function: ripple clock (RCO)\ and maximum/minimum (MAX/MIN) count. MAX/MIN produces a high-level output pulse with a duration approximately equal to one complete cycle of the clock while the count is zero (all outputs low) counting down, or maximum (9 or 15) counting up. RCO\ produces a low-level output pulse under those same conditions, but only while CLK is low. The counters can be cascaded easily by feeding RCO\ to CTEN\ of the succeeding counter if parallel clocking is used, or to CLK if parallel enabling is used. MAX/MIN can be used to accomplish look ahead for high-speed operation.

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Technical documentation

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Type Title Date
* Data sheet SN54HC191, SN74HC191 datasheet (Rev. D) 02 Oct 2003
* SMD SN54HC191 SMD 5962-86891 21 Jun 2016
Application note Implications of Slow or Floating CMOS Inputs (Rev. E) 26 Jul 2021
Selection guide Logic Guide (Rev. AB) 12 Jun 2017
Application note Understanding and Interpreting Standard-Logic Data Sheets (Rev. C) 02 Dec 2015
User guide LOGIC Pocket Data Book (Rev. B) 16 Jan 2007
Application note Semiconductor Packing Material Electrostatic Discharge (ESD) Protection 08 Jul 2004
User guide Signal Switch Data Book (Rev. A) 14 Nov 2003
Application note TI IBIS File Creation, Validation, and Distribution Processes 29 Aug 2002
Application note CMOS Power Consumption and CPD Calculation (Rev. B) 01 Jun 1997
Application note Designing With Logic (Rev. C) 01 Jun 1997
Application note Input and Output Characteristics of Digital Integrated Circuits 01 Oct 1996
Application note Live Insertion 01 Oct 1996
Application note SN54/74HCT CMOS Logic Family Applications and Restrictions 01 May 1996
Application note Using High Speed CMOS and Advanced CMOS in Systems With Multiple Vcc 01 Apr 1996

Design & development

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Package Pins CAD symbols, footprints & 3D models
CDIP (J) 16 Ultra Librarian
LCCC (FK) 20 Ultra Librarian

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